Male touch fastener element

ABSTRACT

A touch fastener has a base and an array of discrete fastener elements each extending from the base and together forming with the base a contiguous mass of resin. Each discrete fastener element includes a stem rising from the base, and a head overhanging the base from a front side of the stem to a distal edge, the front side of the stem, an underside of the head, and an upper surface of the base together forming, in side profile, a generally curved retention space boundary surface such that the boundary surface forms, at its innermost extent, a retention cavity defined between curvature discontinuities spaced from both the base and the distal edge.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/328,257, filed on Apr. 27, 2010, which is incorporated by referenceherein.

TECHNICAL FIELD

This invention relates to male touch fastener elements configured toreleasably engage fibrous loops, and more particularly to such fastenerelements with stems formed of molded resin.

BACKGROUND

Early male touch fastener products were generally woven materials, withhooks formed by cut filament loops. More recently, arrays of very smalltouch fastener elements have been formed by molding the fastenerelements, or at least the stems of the elements, of resin forming aninterconnecting sheet of material. Typically a series of adjacent rowsof male fastener components forms one side or element of a fastenerclosure and a mating female fastener component provides a field of loopsor anchored fibers with which the male fasteners engage.

In most applications, male fastener elements are designed to releasablyengage with the mating female fastener component. To engage the loops,the male fastener elements must penetrate the field of fibers at leastuntil the tips of the engaging fastener element heads have sufficientlyextended beyond some of the fibers, such that the fibers can be engagedwithin the crooks of the heads.

Subsequent to engagement, retention of an engaged fiber or loop depends,at least for loads within the ability of the loop to resist breakage,upon the head's resistance to distention and/or breakage. Distention isthe opening of the crook under load of an engaged loop. For high cyclelife applications, breakage of loops and heads is undesirable. Thus, theability of the fastening to resist peel loads in such applications isgenerally limited by the ability of the head to resist distention.

Unfortunately, for many applications increasing the rigidity of headsdesigned for maximum loop penetration, to increase their peelresistance, is either undesirable or impractical. For example, manyapplications require a gentle ‘feel’ of the male fastener element arrayagainst the skin.

Further improvements in the overall design of male fastener elements,particularly those formed or molded of resin and arranged in largenumbers upon a surface for engaging loops or fibers, are desired.Preferably, such improved fastener elements will be readily andefficiently manufacturable without great advances in manufacturingmethods.

SUMMARY

In general, various innovative aspects of the subject matter describedin this specification feature a touch fastener that includes a base andan array of discrete fastener elements each extending from the base andtogether forming with the base a contiguous mass of resin, incombination with one or more of the innovative aspects described below.

For example, one innovative aspect features a discrete fastener elementincluding a stem rising from the base, and a head overhanging the basefrom a front side of the stem to a distal edge, the front side of thestem, an underside of the head, and an upper surface of the basetogether forming, in side profile, a generally curved retention spaceboundary surface such that the boundary surface forms, at its innermostextent, a retention cavity defined between curvature discontinuitiesspaced from both the base and the distal edge.

In various implementations, the fastener elements can each optionallyinclude one or more of the following features. At least one of thecurvature discontinuities can be an inflection point along the boundarysurface or a corner. The retention cavity can be bounded by a concavecavity wall. The concave cavity wall can define a constant or variablecurvature radius. For example, the curvature radius can be less than 20percent of an overall height of the fastener element above the uppersurface of the base and/or can be between about 0.001 and 0.003 inch(0.025 and 0.076 mm). The head of each fastener can be a generally flat,circular head having a circumference defined by the distal edge.

Another innovative aspect features a discrete fastener element includinga stem rising from the base, and a head overhanging the base from afront side of the stem to a distal edge, the front side of the stem, anunderside of the head and an upper surface of the base together forming,in side profile, retention space boundary surface such that eachfastener element has a ratio of peel thickness, measured along a line 45degrees to the upper surface of the base and normal to the boundarysurface at a point of intersection with the boundary surface, to anelevation of the point of intersection measured from the upper surfaceof the base, that is greater than 0.75 (in some examples, greater than0.85).

In some cases, the elevation of the point of intersection is about halfof the overall height of the fastener element above the upper surface ofthe base.

Another innovative aspect features a discrete fastener element includinga stem rising from the base, and a head overhanging the base, the stem,underside of the head, and an upper surface of the base together forminga retention space boundary surface having a region of innermost extentsuch that the region of innermost extent is spaced above the uppersurface of the base, and such that the stem has a thickness, measuredparallel to the base at the region of innermost extent in a verticalplane intersecting the boundary surface, that is at least twice anelevation of the region of innermost extent above the upper surface ofthe base.

Yet another innovative aspect features a discrete fastener elementincluding a stem rising from the base, and a head overhanging the baseand having a distal tip directed along the row of the fastener element,the stem, an underside of the head, and an upper surface of the basetogether forming a retention space boundary surface having a region ofinnermost extent such that the region of innermost extent is spacedabove the upper surface of the base and such that the stem has athickness, measured parallel to the base at the region of innermostextent, that is at least 1.7 times an elevation of the region ofinnermost extent above the upper surface of the base.

In some examples, the boundary surface forms, at its innermost extent, aretention cavity defined between curvature discontinuities spaced fromboth the base and the distal edge.

In some cases, the elevation of the point of intersection is about halfof the overall height of the fastener element above the upper surface ofthe base.

The head of each fastener, for some applications, is a generally flat,circular head having a circumference defined by the distal edge.

The various inventive aspects described above can be combined forparticular advantage in different embodiments. Additionally, embodimentsmay be provided with other features. For example, the fastener elementscan have at least one flat side. The distal edge of each of the fastenerelements can be a distal tip, such as a non-reentrant tip (i.e., onethat extends generally parallel to or away from the base). Each fastenercan include two or more distinct, distal tips. The boundary surface canbe generally curved. The innermost extent of the boundary surface or theregion of innermost extent can be disposed at an elevation above theupper surface of the base that is less than half of an overall height ofthe fastener element above the upper surface of the base. An innermostextent of the boundary surface and/or the retention cavity and aforward-most portion of the distal edge/tip can form a line extending atbetween about 20 and 40 degrees to the base, and preferably 30 degreesto the base.

Some aspects of the invention feature a retention cavity or pocketformed by a generally curved boundary surface on a front side of thestem. In general, it is realized that the curved boundary surfaceeffectively gathers fibers or loops with which the fastener element isengaged, directing them into the pocket. In this way, retention of theengaged fiber or loop, and the corresponding peel resistance of thefastener component, may be improved.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B are perspective and top views, respectively, of an arrayof discrete fastener elements.

FIGS. 2A, 2B and 2C are side and front views of a discrete fastenerelement.

FIGS. 3 and 4 are side views of alternative implementations of adiscrete fastener element.

FIGS. 5A and 5B are side and front views, respectively, of an exemplarpalm tree implementation.

FIG. 6 is a perspective view of an exemplar mushroom implementation.

FIGS. 7A and 7B are side and front views, respectively, of an exemplarJ-hook implementation.

FIGS. 8, 9 and 10 are schematic views of systems for forming hookmembers using a mold roll.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Referring to FIGS. 1A and 1B, a male touch fastener component 100includes an array of discrete fastener elements 102 arranged in rows 106extending outwardly from a sheet-form base 104, and together formingwith base 104 a contiguous mass of resin. Each fastener element 102includes a head 110 having a non-reentrant tip 111 and extending from astem 120. A non-reentrant tip, as used herein, generally refers to a tipthat extends away from stem 120, substantially parallel to or away froman upper surface 105 of base 104. Fastener elements 102 are engageablein two directions along a plane (i.e., an engagement plane)perpendicular to sheet-form base 108 in the direction of rows 110.

Male fastener component 100 is designed to, for example, strongly engagea low pile height, loop touch fastener component, particularly a loopcomponent with loops formed of inexpensive knit or nonwoven materials.Inexpensive knit or nonwoven materials are desirable for fasteners formass-produced, disposable products such as infant care products,personal care and medical products and packaging requiring low cyclelife. Nonwoven loop materials are constructed, for instance, of a layerof fibers or filaments that have relatively raised or lofty loop regionsbetween regions secured by adhesives or self-adhesive bonds. There isparticular need in these cases for the hook component to be low-costwhile having dependable fastening properties.

Referring now to FIGS. 2A, 2B, and 2C, fastener element 102 has asubstantially constant thickness from base to tip, and includes a stem120 rising from a base 104, and a head 110 overhanging the base from afront side 121 of stem 120 to a distal edge, i.e. tip 111. A generallycurved retention space boundary surface 130 is formed, in side profile,by front side 121 of stem 120, an underside 112 of head 110, and anupper surface 105 of base 104. Boundary surface 130 forms, at itsinnermost extent 131, a retention cavity 134 defined between curvaturediscontinuities 132, 133 spaced from both base 104 and distal tip 111.

In various implementations, curvature discontinuities 132, 133 are of asingle type. For example, FIG. 3 illustrates an alternativeimplementation of a fastener element 302 in which the curvaturediscontinuities include inflection points 332, 333 at which boundarysurface 130 changes from being concave upwards (i.e., positivecurvature) to concave downwards (i.e., negative curvature), and viceversa. In contrast, FIG. 4 illustrates an implementation of a fastenerelement 402 in which the curvature discontinuities are different andinclude a sharp corner 433 and rounded corner 432. As illustrated inFIGS. 3 and 4, some implementations include a deeper and/or lowerretention cavity 134. These and other characteristics vary betweenimplementations to achieve varying degrees of performance with respectto peel resistance and/or to mitigate loop breakage.

Referring again to FIG. 2B, retention cavity 134 is bound by a concavecavity wall 135. In some implementations, concave cavity wall 135defines a constant curvature radius 136. In particular, some examplesinclude a constant curvature radius 136 of less than 20 percent of anoverall height 150 of fastener element 102 above upper surface 105 ofbase 104. In other examples, curvature radius 136 varies (i.e., thedistance as measured in side profile from inner most extent 131 ofboundary surface 130 to concave cavity wall 135). For example, asillustrated in FIG. 4, a variable curvature radius 136, as measured inside profile, increases from corner 432 to corner 433. In each of theexamples, the curvature radius is preferably between about 0.001 and0.003 inch.

In particular implementations, the height, depth, and size of retentioncavity 134 and overall dimensions of fastener element 102 are molded toachieve a desired peel thickness, stem thickness, and/or to achieve adesired ratio of these parameters to the overall dimensions of thefastener element.

Peel thickness, as used herein, is defined as the thickness of fastenerelement 102 as measured in side profile along a line 45 degrees to theupper surface of the base and extending from the front side of the stemto the back of the head, such that the line is normal to the front sideof the stem at a point of intersection. For example, in FIG. 2A, line161 forms a 45 degree angle 163 to upper surface 105 of base 104 andextends from front side 121 of stem 120 to the back of head 110 suchthat line 161 is normal to the front side of stem 120 at a point ofintersection 160. The point of intersection in FIG. 2A is withinretention cavity 134. In some implementations without a retentioncavity, the point of intersection occurs at a point along boundarysurface 130.

In some embodiments, each fastener element 102 has a ratio of peelthickness to an elevation 162 of point of intersection 160 (measuredfrom upper surface 105 of base 104) that is greater than 0.75, andpreferably greater than 0.85. Further, in some examples, innermostextent 131 of boundary surface 130 is disposed at an elevation 165 aboveupper surface 105 of base 104 such that elevation 165 is less than halfof the overall height 150 of fastener element 102 above the uppersurface of the base. Still further, in some embodiments, head 110 ismolded such that innermost extent 131 of boundary surface 130 and aforward-most portion of distal tip 111 form a line 166 extending at anangle 167 having a value of between about 20 and 40 degrees to base 104,and preferably 30 degrees.

In various implementations, fastener element 102 includes a stemthickness 164, measured parallel to base 104 at a region of innermostextent 137 in a vertical plane 138 intersecting boundary surface 130,that is at least twice an elevation 165 of the region of innermostextent above the upper surface of the base. In some implementationshaving distal tip 111 directed along the row 106 of fastener element102, stem 120 has a thickness 164 that is at least 1.7 times anelevation 165 of the region of innermost extent above the upper surfaceof the base.

For some applications, the innovative aspects described herein arecombined with other fastener shapes, such as ‘palm-trees’, mushrooms,and J-hooks. For example, FIGS. 5A and 5B illustrate a ‘palm-tree’fastener 502 including two distal tips 111 and two retention cavities134 spaced away from distal tips 111 and base 104. FIG. 6 illustrates amushroom type fastener 602 including a flat, circular head 110 having acircumference defined by a concave distal edge 111. In variousimplementations, including that of FIG. 6, mushroom fastener 602includes a continuous retention cavity 134 formed around the perimeterof stem 120 and spaced away from distal edge 111 and upper surface 105of base 104. FIGS. 7A and 7B illustrate a J-hook fastener 702 includinga tapered, re-entrant tip 111, a retention cavity 134, and generallycurved sides 770, 772.

Referring again to FIG. 6, a mushroom type fastener element 602 includesa stem 120 extending from a base 104, and a head 110 overhanging base104, stem 120, an underside 112 of head 110, and an upper surface 105 ofbase 104 together forming a retention space boundary surface 130 havinga region of innermost extent 131 such that the region of innermostextent 131 is spaced above upper surface 105 of base 104, and such thatstem 120 has a thickness 164, measured parallel to base 104 at theregion of innermost extent 131. In some implementations, thickness 164is at least twice an elevation 165 of the region of innermost extent 131above upper surface 105 of base 104.

Each of fastener elements of FIGS. 1A-7B can be molded into the shapesshown using one or more techniques. For example, FIG. 8 illustrates amolding technique in which thermoplastic resin 800 is extruded as amolten sheet from extruder 802 and introduced into nip 804 formedbetween a pressure roll 806 and a counter-rotating mold roll 808defining fastener element-shaped cavities in its surface. Pressure inthe nip causes thermoplastic resin 800 to enter blind-ended formingcavities to form the fastener elements, while excess resin remains aboutthe periphery of the mold roll and is molded between the rolls to formsheet-form base 104. The thermoplastic resin is cooled as it proceedsalong the periphery of the mold roll, solidifying the fastener elements,until it is stripped by stripper roll 812. The molded fastener elementsdistend during de-molding, but tend to recover substantially theiras-molded shape. It is generally understood that fastener element crooksmolded to face downstream tend to distend slightly more than thosemolded to face upstream, and can remain more distended in the finalproduct. The direction of travel of the material illustrated in FIG. 8is referred to as the “machine direction” (MD) of the material anddefines the longitudinal direction of the resulting product, while thecross-machine direction (CD) is perpendicular to the machine directionwithin the plane of the sheet-form base. Further details regardingprocessing are described by Fischer, U.S. Pat. No. 4,775,310 and Cluneet al., U.S. Pat. No. 6,802,260, the disclosures of which are herebyincorporated in full by reference.

In some embodiments, the mold roll 808 comprises a face-to-face assemblyof thin, circular plates or rings (not shown) that are, for example,about 0.003 inch to about 0.250 inch (0.0762 mm-6.35 mm) thick, somehaving cutouts in their periphery defining mold cavities and othershaving solid circumferences, serving to close the open sides of the moldcavities and serve as spacers, defining the spacing between adjacentfastener element rows. A fully “built up” mold roll may have a width,for example, from about 0.75 inch to about 6 inches (1.91 cm-15.24 cm)or more and may contain, for example, from about 50 to 1000 or moreindividual rings. Further details regarding mold tooling are describedby Fisher, U.S. Pat. No. 4,775,310. Additional tooling embodiments willalso be described below.

The cavities that made the fastener element shown in FIG. 1A-5B havesharp edges and straight sidewalls (e.g., see sidewalls 170, 172 shownin FIGS. 2C and 5B) and create fastener elements with substantiallysimilar cross-sections through the thickness of the fastener element.Tooling with straight sidewalls and edges can be made by, for example,laser cutting, wire EDM or electroforming. Further details regardinglaser cutting and wire EDM mold tooling is described by Fisher, U.S.Pat. No. 4,775,310. The electroforming process is described by Clarneret al., U.S. Pat. No. 7,052,638, the disclosure of which is herebyincorporated in full by reference.

By contrast, fastener elements formed in cavities that have been, forexample, photochemically etched may have rounded surfaces in some or allregions, from base to tip, such as the fasteners illustrated in FIGS.6-7B. For example, surfaces at the top of the heads can be made to taperto a point to give a wedge effect. A wedge-shape may, for example,assist the entry of the crook into the face of a mating female fastenercomponent. Further details regarding photochemical etching is describedin Lacey et al., U.S. Pat. No. 6,163,939, the entire disclosure of whichis hereby incorporated in full by reference.

An alternate technique for molding fastener elements is shown in FIG. 9.The process is similar to that described above with reference to FIG. 8,except only a mold roll 808 is used, i.e., no pressure roll 806 isnecessary. Here, the extruder 802 is shaped to conform to the peripheryof the mold roll 808 and the extruded resin 800 is introduced underpressure directly to a gap 814 formed between mold roll 808 and extruder802. The molded fastener component is stripped from the mold cavities bya stripper roll 812 as described above. Further details regarding thisprocess are described by Akeno, U.S. Pat. Nos. 5,781,969 and 5,913,482,the disclosures of which are hereby incorporated in full by reference.

Referring to FIG. 10, a laminated male touch fastener component 101 maybe formed by introducing a pre-form material 815 into nip 804 betweenthe mold and pressure rolls. As a result of the heat and pressure in nip804, pre-form material 815 becomes laminated and bonded to thethermoplastic resin 800 simultaneously with the forming of the fastenerelements. The result can be a contiguous molded structure, without weldlines, extending from the tips of the fastener elements into thepre-form material, where the resin can intimately bond with features orfibers of the material to form a strong, permanent bond. Further detailsregarding this process are described by Kennedy et al., U.S. Pat. Nos.5,260,015, the disclosures of which is hereby incorporated in full byreference.

In one useful embodiment, pre-formed material 815 is a loose knit scrim,such as Knit 3901 from Velcro USA in Manchester, N.H., although VelcroUSA loop products 3900, 3905, and 3400 may also be employed. Thesefabrics are 2 bar tricot knit fabrics, whose technical back sides aretypically brushed or napped to raise the surface floats and create ahook-engageable loop surface. Knit 3901 is a similar 2 bar Tricot knitnylon fabric which generally must be brushed or napped before it can beemployed as the functioning loop of a hook and loop closure. However, ithas been found to function well as a reinforcement when at leastpartially encapsulated by, or bonded to, the base resin contiguous withthe resin forming the hooks, without brushing or napping. Reinforcingthe base with such a scrim has been found to improve the stitch tearstrength of the product, providing a resin-base hook product practicalfor attachment by sewing or stitching.

Referring back to FIGS. 8-10, in some cases, the fastener elements arenot molded in their final form. In any of the methods disclosed above,for example, the fastener component may be routed through subsequentprocessing station 830 to finalize the form of the fastener elements.Such subsequent processing may include “flat-topping” overhangingfastener element preforms, as described by Provost, U.S. Pat. No.5,953,797, and Akeno, U.S. Pat. No. 5,781,969, the disclosure of both ofwhich is hereby incorporated in full by reference. In some cases, evenstraight molded stems may be subsequently processed to result infastener elements having the properties disclosed herein. Flat-sidedfastener elements with the profiles shown in FIGS. 2C and 5B can also beformed by a cut-and-stretch method, such as the method disclosed inNestegard, U.S. Pat. No. 4,895,569, for example. In such processes,moldable resin is extruded through a die with openings shaped in thedesired hook profile, then the extruded rails are cut transverse to theextrusion direction, and the base stretched in the extrusion directionto separate the rails into rows of discrete fastener elements. Thisprocedure results in fastener elements with broad sides that are cutrather than molded, as in the processes described above, and withprofile edges formed by sliding resin through a shaped die rather than afilling cavity.

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention.Accordingly, other embodiments are within the scope of the followingclaims.

What is claimed is:
 1. A touch fastener comprising: a base; and an arrayof discrete fastener elements each extending from the base and togetherforming with the base a contiguous mass of resin; wherein each of thefastener elements comprises: a stem rising from the base; and a headoverhanging the base from a front side of the stem to a distal edge, thefront side of the stem, an underside of the head, and an upper surfaceof the base together forming, in side profile, a generally curvedretention space boundary surface; wherein the boundary surface forms, atits innermost extent, a retention cavity defined between curvaturediscontinuities spaced from both the base and the distal edge.
 2. Thetouch fastener of claim 1, wherein at least one of the curvaturediscontinuities is an inflection point along the boundary surface. 3.The touch fastener of claim 1, wherein at least one of the curvaturediscontinuities is a corner.
 4. The touch fastener of claim 1, whereinthe retention cavity is bounded by a concave cavity wall.
 5. The touchfastener of claim 4, wherein the concave cavity wall defines a constantcurvature radius.
 6. The touch fastener of claim 1, wherein each of thefastener elements has at least one flat side.
 7. The touch fastener ofclaim 1, wherein each of the fastener elements comprises two distaltips.
 8. The touch fastener of claim 1, wherein the head is a generallyflat, circular head having a circumference defined by the distal edge.9. The touch fastener of claim 1, wherein the innermost extent of theboundary surface is disposed at an elevation above the upper surface ofthe base that is less than half of an overall height of the fastenerelement above the upper surface of the base.
 10. The touch fastener ofclaim 1, wherein the distal edge is a non-reentrant distal tip.
 11. Thetouch fastener of claim 1, wherein an innermost extent of the boundarysurface and a forward-most portion of the distal edge form a lineextending at between about 20 and 40 degrees to the base.
 12. A touchfastener comprising: a base; and an array of discrete fastener elementseach extending from the base and together forming with the base acontiguous mass of resin; wherein each of the fastener elementscomprises: a stem rising from the base; and a head overhanging the basefrom a front side of the stem to a distal edge, the front side of thestem, an underside of the head and an upper surface of the base togetherforming, in side profile, a retention space boundary surface; whereineach fastener element has a ratio of peel thickness, measured along aline 45 degrees to the upper surface of the base and normal to theboundary surface at a point of intersection with the boundary surface,to an elevation of the point of intersection measured from the uppersurface of the base, that is greater than 0.75.
 13. The touch fastenerof claim 12, wherein the boundary surface is generally curved.
 14. Thetouch fastener of claim 12, wherein the boundary surface forms, at itsinnermost extent, a retention cavity defined between curvaturediscontinuities spaced from both the base and the distal edge.
 15. Thetouch fastener of claim 12, wherein the elevation of the point ofintersection is about half of an overall height of the fastener elementabove the upper surface of the base.
 16. The touch fastener of claim 12,wherein each of the fastener elements has at least one flat side. 17.The touch fastener of claim 12, wherein the head is a generally flat,circular head having a circumference defined by the distal edge.
 18. Thetouch fastener of claim 12, wherein an innermost extent of the boundarysurface is disposed at an elevation above the upper surface of the basethat is less than half of an overall height of the fastener elementabove the upper surface of the base.
 19. The touch fastener of claim 12,wherein the distal edge is a non-reentrant distal tip.
 20. The touchfastener of claim 12, wherein an innermost extent of the boundarysurface and a forward-most portion of the distal edge form a lineextending at between about 20 and 40 degrees to the base.